The Hybridoma and Tissue Culture Shared Resource makes monoclonal antibodies (mAbs), assists in the characterization and production of mAbs in vitro and in vivo, makes standard tissue culture media, and instructs members in the use of phage peptide display libraries. The facility maintains and distributes phage libraries and special cell lines used in the hybridoma technology, maintains ELISA readers and plate washers for use by AECCC investigators and backup cell freezers for investigators who have made hybridomas or obtained them elsewhere. The facility maintains tissue culture media and serum screened to give high cloning efficiencies for hybridomas and prescreens and standardizes serological reagents used to characterize mAbs. In 1997 the facility established a SCID mouse colony for in vivo production of mAbs not contaminated by other antibodies and has assisted AECCC members in this process. The facility makes available to AECCC members the repertoire of technologies and reagents that have been developed in individual AECCC member research laboratories. These include, for example; (I) the use of phage display libraries to identify epitopes and the use of peptides from phage libraries as substitutes for antibodies; (ii) the use and distribution of the NSObcl-2 fusion partner developed by Dr. Diamond for antigens that elicit large numbers of autoantibodies that will nevertheless be useful reagents; (iii) isotype switching in tissue culture, developed by Dr. Scharff, to convert a mAb from one isotype to another. Recently, the facility has tested both gas-permeable bags (Baxter) and CELLine (Integra Biosciences) flasks for producing high concentrations of mAb in vitro and is now using CELLine flasks as an alternative to the Cell Max hollow fiber production apparatus. As a result of a National Research Council report and anticipated NIH guidelines, the Einstein Animal Institute Committee has begun to require investigators to justify the production of mAb in vivo as ascites based in part on the amount of mAb that can be efficiently produced in vitro. The facility now determines micro g/106 cells/24hrs of mAb produced from each hybridoma so that investigators can submit that information to the Animal Institute Committee. This allows a rational decision regarding the method of mAb production and justifies the use of ascites if that is necessary.